The influenza A virus is a well characterized virus that infects humans as well as a large number of other species. See, e.g., U.S. Patent Publication No. 20050186621. All of the sixteen subtypes of influenza A virus circulate in wild birds and domestic avian species. Few influenza subtypes are epidemic among humans, but periodically pandemic strains derived from animals or birds unpredictably emerge causing wide spread disease of high morbidity and mortality.
The influenza A virus (H1N1) 1918 was the most virulent and highly contagious airborne pathogen in the recorded history of human infectious diseases. After the 1918 pandemic, this virus gradually changed to a less virulent strain and with time the original highly pathogenic virus no longer circulated in humans. However, given the vast reservoir of influenza viruses in wild bird populations as well as the complex epidemiology, biology and evolutionary characteristics of this virus it is possible that a similar or related strain will reemerge creating a serious threat to global public health. In addition, the recent re-creation of this pathogen raises serious concern that the available technology could lead to reconstruction of this virus as a biological weapon.
Avian influenza viruses are also a constant threat to humans because of cross-species transmission which allows for their adaptation to humans through mutations or reassortment with the potentially of causing a global pandemic. Avian to human transmission has resulted in more than 300 human cases of avian influenza worldwide with a mortality rate close to 40%. See, Thomas & Noppenberger (2007) Am J Health Syst Pharm. 64(2):149-65, Epidemiology of WHO-confirmed human cases of avian influenza A(H5N1) infection. Wkly Epidemiol Rec. 2006 Jun. 30; 81(26):249-57. Indeed, since 1997, the avian influenza virus H5N1 has been causing massive disease outbreak in domestic poultry as well as in other avian and mammalian species. In addition, a recent outbreak of the highly pathogenic avian influenza subtype H7N7 in the Netherlands resulted in multiple human infections, one of which proved fatal.
Traditionally, influenza vaccines are produced in fertilized chicken eggs. Eleven days after fertilization, a single strain of influenza virus is injected into the eggs. The virus multiplies in the infected embryo and after several days of incubation, the eggs are opened the virus harvested with the fluid surrounding the embryo, purified, chemically inactivated and combined with other similarly produced strains to generate an influenza vaccine. On average, one to two eggs are needed to produce one dose of vaccine and the entire production process lasts at least six months. Given the long production times, it is unlikely that egg-based production of flu vaccines could be used to contain a flu pandemic.
Therefore, there remains a need for compositions and methods that prevent and/or treat infection with the various highly virulent and transmissible influenza strains.